May 8, 2013

With reduced precipitation and soil moisture in some areas, alfalfa growers may want to start irrigating before the first cutting this year.

Consider a pre-season irrigation if your soil is dry, as is common in central and western Nebraska. In fact, early spring often is the best time to irrigate alfalfa because it's about the only time you can build a reserve water source for use later in the summer.

Alfalfa can develop roots more than eight feet deep, if necessary, to find soil moisture. Deep roots that are in deep moisture will make your summer irrigating much easier by providing extra moisture when plants use as much as 0.5 inch per day. Conversely, typical shallow watering during summer encourages shallow rooting.

The biggest advantage of having a reserve of deep water comes after each summer cutting. Alfalfa roots need oxygen in the soil if plants are to regrow rapidly. Irrigating right after cutting suffocates roots, slowing down regrowth. Immediate watering also stimulates shallow rooted or sprouting weeds, especially at a time when alfalfa plants are not very competitive. Both problems are reduced when water is available for deep alfalfa roots while the top several inches of soil remain dry. After alfalfa regrows several inches it will out-compete most weeds so irrigation can begin again.

Improve your alfalfa this season by irrigating early with a goal of having six to eight feet of soil at field capacity for soil moisture by the first cutting.

Bruce Anderson
Extension Forage Specialist